Abstract: Why are some students, athletes, and musicians more successful than others? People tend to have intuitive feelings about the root source of variance in success. These feelings reflect the cultural milieu of the time and the corresponding trend in psychology--from biological determinism to environmental determinism, to, I will argue, today's self-determinism. Two current popular theories of achievement, deliberate practice and mindset, are exemplars of the current view. Each theory has made bold claims about how their respective ideas have profound effects on achievement. As each theory gained popularity, they influenced policies, practices, and parenting decisions. But does the evidence support their strong claims? Might there be potential harms of implementing programs based on the theories? If these theories are not backed by evidence, there may be specific cognitive fallacies responsible for their continued popularity.